1. Field of the Invention
This invention relates to an anion adsorption carbon material for adsorbing anions such as nitrate ions and fluoride ions, as well as a manufacturing method and manufacturing facilities for the same.
2. Description of Related Art
Contamination of water quality and soil by heavy metals, agricultural chemicals and organochlorine compounds has become a problem in that it destroys the environment. Though these harmful substances can be adsorbed and removed with adsorbents such as activated carbon and a zeolite, it is presently difficult to treat nitrate nitrogen, nitrite nitrogen, fluorine, arsenic and cyan which exist in the form of anions with adsorbents.
Nitrate nitrogen and nitrite nitrogen are usually included in fertilizers used in tea fields, turfs for golfing and the like, and have become a factor in ground water contamination, which is presently a large problem. This is because nitrate ions and nitrite ions have a negative charge and do not become an insoluble salt by combining with other chemical substances, and therefore, very easily wash out from negatively charged soil. Thus, although measures against the above described problem are frequently required, there are practical limitations, such that anaerobic conditions are required in biological treatment where, for example, denitrifying bacteria are used to remove nitrate ions and nitrite ions, and in addition, there are similar limitations with other methods. Thus, no completely effective measures have been found. On top of this, recently, it has come to be believed that nitrate nitrogen and nitrite nitrogen are possible environmental hormones.
In addition, fluorine is included in wastewater from semiconductor factories, glass factories, plating factories and the like, and although a method for adding calcium compounds to fluorine in industrial wastewater so that the fluorine can be removed in the form of calcium fluorine has been used, further installation of adsorption towers having an anion exchange resin for active alumina and fluorine is required, thereby raising the cost. In addition, expensive dedicated anion exchange resins are required in order to meet governmental regulations such as a Japanese environmental standard of 0.8 mg/L. Furthermore, expensive anion exchange resins are separately required for treating arsenic, cyan and the like which are also found in industrial wastewater and ground water.
As described above, no inexpensive material for adsorbing anions including nitrate ions as described above have been found at present, and therefore, contamination by these anions tend to spread, and once the environment is contaminated by anions as described above, high cost becomes necessary to restore it, see Japanese Unexamined Patent Publication H10 (1998)-165824